Self-lowering jack



F. H SCHWERIN.

SELF LOWERING JACK.

APPLICATION FILED FEB. 4,192].

82. Patented Nov. 22, 1921,.

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SELF LOWERING JACK.

APPLICATION FILED FEB- 4. 1921.

1,397,882. Patented Nov. 1921.

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Sum/M501 53 elite snag UNITED STATES PATENT OFFICE.

FRANK H. SCHWERIN, OF WESTVIEW BOROUGH, PENNSYLVANIA, ASSIGNOR TO THE DUFF MANUFACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPO- RATION OF PENNSYLVANIA.

SELF-LOWERING JACK.

Application filed February 4, 1921.

T (ZZZ whom it may concern Be it known that I, FRANK H. SCHWERIN, a citizen of the United States, and a resident of the borough of \Vestview, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Self-Lowering Jack, of which the following is a specification.

This invention relates to self-lowering screw-jacks, and more particularly to that kind in which the load is lifted by steeppitch screw means capable of running down under the load, and held and lowered by hydraulic means. The object is to provide a jack of this type having important simplicity and eflieient in operation.

In the accompanying drawings, forming a part hereof:

Figure 1 is a vertical section through a jack embodying the invention, the outer part of its operating shaft being broken away;

Fig. 2 is an elevation looking at right angles to Fig. 1, with portions broken away and in section; a

Fig. 3 is a horizontal section on the line 3 of Fig. 1; and

Fig. 4 is a similar section on the line 4-4 of Fig. 1.

The jack illustrated in these views comprises a closed base 1 having an upstanding hollow standard 2 with a bearing 3 in its top, and a vertically movable cylindrical load member or ram 4 slidably guided in the bearing.

A vertical screw 7 having a bevel gear 8 upon its lower portion is rotatably supported on the removable bottom plate 9 of the base, by means of a ball thrust bearing 10, and passes upward through a nut 11, or female nut part, formed on or secured in the lower end of the load member 4. The threads of the screw parts are of steep-pitch, that is to say. beyond the angle of repose, so that they will permit the load member to descend under the action of the load, the nut in this instance rotating the screw, and the remainder. of the operating mechanism being such as to permit this action.

Operating means for the screw may comprise the bevel gear 8 and a bevel pinion 12 on a horizontal operating or lifting shaft 13 passing through a bearing 14 in the wall of the base, on the outer end of which shaft Specification of Letters Patent.

Patented Nov. 22, 1921.

Serial No. 442,361.

is a pivoted pawl rocker 15, having .the usual socket 16 for the reception of a lever handle. A pawl 17 pivoted on the rocker engages a customary ratchet wheel 18 fixed on the shaft, the pawl being pressed by a spring plunger l9,which will also hold the pawl out of action for lowering.

The load member is constructed so that its hollow interior 22 forms a hydraulic cylinder, in which is a stationary piston 24L on the upper end of the screw 7. The liquid chamber 27 of the cylinder between the piston and the head of the load member thus extends as the load member rises and contracts as it descends. The cylinder, employing this term in the inclusive sense, comprehending the relatively movable piston and cylinder, or equivalent, parts, together forming an enlarging and contracting fluid chamber, is interposed between the base and load members of the jack, with its relatively movable parts respectively thereon, the cylinder part, as illustrated, being on the load member, and the piston part on the screw, which in turn is supported on the base member. The cylinder is more especially a fluid-pressure-tight cylinder capable of sustaining the load on the load member. A cup packing 25, secured by a plate 26 to the piston makes a tight sliding joint with the smooth wall of the cylinder, adapted to hold against pressure in the chamber 27. Air vent passages 28 in} the head of the ram, forming the upper end of the cylinder, permit the escape of trapped air from the liquid chamber, and are automatically closed by a valve 29 which is lifted by a float 29 against a seat 30 when the chamber is filled with liquid admitted through a passage 31.

A pump cylinder is also arranged between and with .its relatively movable parts on the two jack members, to supply the chamber 27 of the first cylinder with liquid when the load member and load are lifted by the screw. In the illustrated embodiment the upper or standard part 2 of the base member is formed with a cylindrical interior 32 materially wider than the opening in the top-bearing 3, and the lower end of the ram 4 is formed or provided with an annular piston enlargement 33, which has a tight sliding fit with the smooth stationary Wall. Packings 34 are placed upon of the base member.

this piston, and another packing 34 in the bearing to cooperate with the smooth exterior of the ram. An annular pump chamber is thus formed beneath the top bearing, which contracts as the holding and lowering chamber 27 enlarges, and viceversa. The capacity of the chamber 35 is said passage closes against outflow from the chamber 27, while perm tting free ingress when the ram ascends.

The base member 1 is made tight to constitute a reservoir 39 for lubricating oil, with which the chambers 27 and 38 have communication, or other suitable liquid reservoir might be providedl An intake passage 40 extends upward from the lower part of the reservoir to the upper part of the pump chamber 35, where it opens by a port 41 through the wall of thestandard portion The said intake passage may be formed largely or in part by a pipe, as shown, fixed on the base member and passing through a gland 42 in the top of the enlarged lower portion thereof, or it may be otherwise constituted. An automatic check valve-43 commanding the intake permits free passage of liquid from the reservoir to the pump chamber'35 when the load member descends, but closes against exit when the said member ascends, the liquid in the contracting pump cylinder chamber being then forced to flow through the passage 31 to the enlarging chamber 27.

Another passage 44 is formed through the lower, piston portion of the load member 4, to vent excess liquid from the pump chamber 35 back into the general reservoir 39, this passage being controlled by an automatic valve 45 closing toward the pump chamber and loaded by a spring 46 which is stronger than the spring 47 of the check-valve 38 interposed in the passage 31 between the chambers 27 and 35. q

When the load member is permitted to move downward under the action of the load, the liquid in the chamber 27 escapes downward through a longitudinal passage 48 extending through the screw 7 The lower end of this screw is received in a chamber 49 in the bottom plate 9 ofthe base member, beneath the ball-bearing 10, and from this chamber an angular passage 50 extends in said plate or wall, terminating in an open ing 51 through the top of the plate into the main reservoir. a header into which the passage 48 in the screw opens, maintaining communication between thispassage and the passage 50, and is made tight against leakage therefrom, by

The chamber 49 constitutes.

a cup packing 52 at the top of the chamber,

through a stuffing-box 56, and provided at its outer end with a hand-wheel 57, the tapered point ofthe valve coacting with an appropriate seat in the passage 50,

In operation, the load isv lifted by ratcheting the operating shaft step-by-step by means of the operating lever. This through the gears 12 and 8 rotates the screw 7 in the direction to move the nut 11 upward, thereby raising the load member and load. Thepump chamber 35 being full of liquid, the liquid therein is forced through the passage 31 into the chamber 27, past the check-valve 38. At any point the load is sustained by the liquid in this tight chamber, the checkvalve preventing the liquid returning through the supply passage and the closed manual valve 55 preventing it escaping by way of the passage 48 in the screw. Airif present in the chamber 27 is automatically allowed to escape through the air vent passagesv28, but the liquid cannot escape .at this point when the chamber is full because the float closes the valve 29. Liquid beyond that needed to keep the, chamber 27 filled as the load member ascends is vented through the excessliquid passage 34 and past the loaded valve 45 into the main reservoir in the base. In order to lower the load, the valve 55 is opened, allowing the liquid in the chamber 27 to pass gradually out through the bore of the screw and the passageway in the bottom plate back to the reservoir. The rate of escape and thereby the speed of lowering can be regulated by manipulation of the valve handle 57. Closing the valve again causes the load to stop and holds it. The lowering operation automatically causes liquid to ascend from the reservoir through the passage 40 and past the check-valve 43 into the enlarging pump chamber, refilling this chamber.

,lVhat is claimed as new is:

1. A self-lowering jack having closed base and load members, steep-pitch screw mechanism acting between said members to effect lifting, a hydraulic holding cylinder having its relatively movable parts on the respective jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable pump cylinder parts also on the respective jacket members for supplying the holding cylinder chamber with liquid.

2. A. self-lowering jack having closed base and load members, steep-pitch screw mechanism acting between said members to effect lifting, a hydraulic holding cylinder having its relatively movable parts on the respective jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable pump cylinder parts also on the respective jack members for supplying the holding cylinder chamber with liquid, one of said jack members havin in it a passage connecting the pump cylinder and holding cylinder chambers, with a check-valve controlling said passage.

3. A self-lowering jack having closed base and load members, steep-pitch screw mechanism acting bet-ween said members to effect lifting, a hydraulic holding cylinder having its relatively movable parts onv the respective jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable cylinder parts also on he respective jack members for suo l in the holdin c linder chamber,

lPy s a 3 with liquid, one of said ack members hav ing in it a vent passage from the pump cylinder chamber to the reservoir in the base, and a spring-yielding valve for said passage,

i. A. self-lowering jack having closed base and load members, steep-pitch screw mechanism acting between said members to effect lifting, a hydraulic holding cylinder having its relatively movable parts on the respec tive jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable pump cylinder parts also on the respective jack members for supplying the holding cylinder chamber with liquid, there being an intake passage from the lower part of the interior of the base member to the pump cylinder chamber.

5 A self-lowering jack having closed base and load members, steep-pitch screw mechanism acting between said members to effect lifting, a hydraulic holding cylinder hav ing its relatively movable parts on the re spective jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable pump cylinder parts also on the respective jack members for supp ying the holding cylinder chamber with liquid, and a stationary intake passage with check-valve from the lower part of the interior of the base member to the upper part of the pump cylinder chamber.

6. A self-lowering jack having closed base and load members, steep-pitch screw mech anism acting between said members to effect lifting, a hydraulic holding cylinder having its relatively movable parts on the respective jack members, and means for opening and closing an outlet from said cylinder chamber to effect lowering and holding of the load, in combination with means comprising relatively movable pump cylinder parts also on the respective jack members forming an annular pump chamber for supplying the holding cylinder chamber with liquid.

7. A self-lowering jack comprising a closed base member having a top bearing, a load member vertically siidable in said bearing and containing a nut, and a rotatable lifting screw on the base member ex tending upward through the nut and like the nut being of steep pitch, the interior of the load member being formed as a hydraulic cylinder, with a stationary piston on the screw, the upper part of the base member cooperating with the load member to form an annular pump cylinder chamber below said bearing, with an annular piston on the lower portion o'l the load member working therein, there being an intake from the reservoir in the base to said annular chamber, a passage from said chamber to the first cylinder chamber, and an escape from said first cylinder chamber for lowering.

S. A self-lowering jack comprising a closed base member having a top bearing, a load member vertically slidable in said bearing and containing a nut, and a rotatable lifting screw on the base member extending upward through the nut and like the nut being of steep pitch, the interior of the load member being formed as a hydraulic cylinder, with a stationary piston on the screw, the upper part of the base member co operating with the load. member to form an annular pump cylinder chamber below said bearing, with an annular piston on the lower portion of the load member working therein, there being an intake from the reservoir in the base to said annular chamber, a passage in the wall of the load member from the annular chamber to the first cylinder chamber, and an escape from the first cylinder chamber for lowering.

9. A self-lowering jack comprising a closed base member having a top bearing, a load member vertically slidable in. said bearing and containing a nut, and a rota table lifting screw on the base member extending upward through the nut and like the nut being of steep pitch, the interior or the load member being formed as a hydraulic cylinder, with a stationary piston on the screw, the upper part of the base member cooperating with the load member to form an annular pump cylinder chamber below said bearing, with an annular piston on the lower portion of the load member working therein, there being an intake from the reservoir in the base to said annular chamber, a passage from said chamber to the first cylinder chamber, an escape from said first cylinder chamber for lowering, and a vent passage in the lower portion of the load member, with an automatic springyielding valve commanding the same.

10. A self-lowering jack, comprising a closed base member, a load member vertically slidable therein and containing a nut, a rotatable lifting screw on the base extending upward through the nut and like the nut being of steep pitch, the interior of the load member being formed as a hypassage communicating with said cylinder draulic cylinder, with a stationary piston on the screw, the screw having a longitudinal passage communicating with said cylinder chamber, and the base containing a tight chamber in its'bottom wall receiving the lower portion of said screw, and a passageway connecting with said chamber.

11. A self-lowering jack, comprising a closed base member, a load member vertically slidable therein and containing a nut, a rotatable lifting screw on the base eX- tending upward through the nut and like the nut being of steep pitch, the interior of the load member being formed as a hychamber, and the base containing a tight chamber in its bottom wall receiving the lower portion of said screw, a passageway connecting with said chamber, and a manually operated valve controlling said passageway.

12. A self-lowering jack, having closec base and load members, steep-pitch screw mechanism between said members to etfect lifting, and a hydraulic cylinder having its relatively movable parts on the respective jack members, in combination with means comprising relatively movable cylinder parts also on the respective jack members forming an annular pump chamber. which contracts as said hydraulic cylinder chamber enlarges in the upward movement of the load member, to supply said hydraulic cylinder with liquid.

13. A self-lowering jack, having base and load members and, interposed steep pitch screw means for lifting, an interposed hydraulic chamber formed by relatively movable parts on the respective jack members so as to enlarge as the load member is raised by the screw means and contract as said member. descends, means for automatically venting air from said chamber,and means for pumping liquid into the chamber as the load member rises.

FRANK H. oHwEmN. 

